Nonaqueous electrolyte secondary batteries are compact, lightweight, high-energy-density batteries with a wide range of applications including power supplies for mobile devices. Recently, these batteries have also attracted attention as power supplies for powering devices such as power tools, electric vehicles, and HEVs. Such power supplies require high-rate discharge characteristics, i.e., the ability to discharge a large current in a relatively short period of time.
PTL 1 discloses that the use of an aluminum foil having a roughened surface facing a positive electrode layer improves the adhesion between the active material layer and the aluminum foil. However, there is a need for a further modification to improve the high-rate discharge characteristics of nonaqueous electrolyte secondary batteries.
PTL 2 discloses that it is advantageous to form a carbon intermediate film on an aluminum foil current collector and form an active material layer thereon to reduce the electrical resistance between the current collector and the active material. Again, in this citation, there is a need for a further modification to improve the high-rate discharge characteristics of nonaqueous electrolyte secondary batteries. This method also has a problem that it requires the steps of forming the carbon intermediate film and forming the active material layer thereon, which complicate the manufacturing process.